High-volume, cost-sensitive work
Choose GPT-5.5
GPT-5.5 costs 44% less on a typical mix of three input tokens for every output token ($11.25 against $20.00 per million tokens).
Claude Fable 5.1 vs GPT-5.5: price, context and capabilities
Choose Claude Fable 5.1 for reused prompts and documents (RAG, agents), the hardest reasoning tasks, the latest release and the most recent knowledge. Choose GPT-5.5 for high-volume, cost-sensitive work and writing and code generation.
In short
- GPT-5.5 is 44% cheaper than Claude Fable 5.1 at the headline price ($11.25 / 1M tokens vs $20.00 / 1M tokens).
- GPT-5.5 reads more per request: 1.05M tokens against 1M.
- Claude Fable 5.1 is the newer model (September 2026, against Apr 24, 2026).
Which should you choose?
Each answer below comes straight from the published prices, specifications and independent benchmark results.
Writing and code generation
Choose GPT-5.5
GPT-5.5 charges $30.00 per million output tokens, against $50.00 for Claude Fable 5.1. Output dominates the bill when answers are long.
Reused prompts and documents (RAG, agents)
Choose Claude Fable 5.1
Claude Fable 5.1 charges $0.25 per million cached input tokens, against $0.50 for GPT-5.5.
Hardest reasoning tasks
Choose Claude Fable 5.1
Claude Fable 5.1 scores 53.4 on the Artificial Analysis Intelligence Index, against 38.4 for GPT-5.5.
Reasoning over long documents
Either one
They are practically level on Long-context reasoning (AA-LCR) (85.3% and 84.3%).
Latest release
Choose Claude Fable 5.1
Claude Fable 5.1 is the newer release (September 2026, against Apr 24, 2026 for GPT-5.5).
Most recent knowledge
Choose Claude Fable 5.1
Claude Fable 5.1 was trained on data up to June 2026, against December 2025 for GPT-5.5.
Monthly cost at three volumes
| Volume | Claude Fable 5.1 | GPT-5.5 | Difference |
|---|---|---|---|
| Prototype: 1M input, 250K output tokens | $22.50 | $12.50 | GPT-5.5, $10.00 less |
| Production: 20M input, 5M output tokens | $450.00 | $250.00 | GPT-5.5, $200.00 less |
| Scale: 500M input, 100M output tokens | $10,000 | $5,500 | GPT-5.5, $4,500 less |
Standard rates, without caching or batch discounts. Volumes are per month.
Specifications side by side
| Claude Fable 5.1 | GPT-5.5 | |
|---|---|---|
| Provider | Anthropic | OpenAI |
| Category | Language models | Language models |
| Status | Generally available | Legacy |
| Headline price | $20.00 / 1M tokens | $11.25 / 1M tokens |
| Input | $10.00 / 1M tokens | $5.00 / 1M tokens |
| Output | $50.00 / 1M tokens | $30.00 / 1M tokens |
| Cached input | $0.25 / 1M tokens | $0.50 / 1M tokens |
| Context window | 1M | 1.05M |
| Max output | 128k | 128k |
| Released | September 2026 | Apr 24, 2026 |
| Knowledge cutoff | June 2026 | December 2025 |
| Licence | Proprietary | Proprietary |
| Capabilities | Vision, Reasoning, Tool calling, Structured output, Prompt caching, Batch API | Vision, Reasoning, Tool calling, Structured output, Prompt caching, Batch API |
| API model id | claude-fable-5-1 | gpt-5.5 |
Benchmarks side by side
Leader in bold.
| Benchmark | Claude Fable 5.1 | GPT-5.5 |
|---|---|---|
| Intelligence Index | 53.4 | 38.4 |
| SciCode | 63.1% | 55.8% |
| GPQA Diamond | 93.7% | 93.5% |
| Humanity's Last Exam | 59.1% | 45.8% |
| Long-context reasoning (AA-LCR) | 85.3% | 84.3% |
| Terminal-Bench Hard | No data | 60.6% |
| IFBench (instruction following) | No data | 75.9% |
| τ²-Bench (agentic tool use) | No data | 93.9% |
| MMMU-Pro (visual reasoning) | No data | 79.9% |
Independent evaluations by Artificial Analysis, run the same way for every model, at the reasoning setting shown. Percentages unless marked as an index.
Frequently asked questions
Should I choose Claude Fable 5.1 or GPT-5.5?
Choose Claude Fable 5.1 for reused prompts and documents (RAG, agents), the hardest reasoning tasks, the latest release and the most recent knowledge. Choose GPT-5.5 for high-volume, cost-sensitive work and writing and code generation.
Which is cheaper, Claude Fable 5.1 or GPT-5.5?
GPT-5.5 is 44% cheaper than Claude Fable 5.1 at the headline price ($11.25 / 1M tokens vs $20.00 / 1M tokens).
Which has the larger context window, Claude Fable 5.1 or GPT-5.5?
GPT-5.5 reads more per request: 1.05M tokens against 1M.
What is the difference between Claude Fable 5.1 and GPT-5.5?
Claude Fable 5.1 is made by Anthropic and GPT-5.5 by OpenAI. GPT-5.5 is 44% cheaper than Claude Fable 5.1 at the headline price ($11.25 / 1M tokens vs $20.00 / 1M tokens). GPT-5.5 reads more per request: 1.05M tokens against 1M. Claude Fable 5.1 is the newer model (September 2026, against Apr 24, 2026).
How much do Claude Fable 5.1 and GPT-5.5 cost per month?
At 20 million input and 5 million output tokens a month, Claude Fable 5.1 costs $450.00 and GPT-5.5 costs $250.00, at standard rates.
Which is newer, Claude Fable 5.1 or GPT-5.5?
Claude Fable 5.1 was released on September 2026 and GPT-5.5 on Apr 24, 2026.